authentication system

package authentication_systems;

import java.io.File;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class AuthenticationSystems {

    public static void main(String args[]) {

        try {
            Scanner scan = null;
            scan = new Scanner(new File("credentials.txt"));
            String credentials[][] = new String[100][4];
            int count = 0;
            while (scan.hasNextLine()) {
//read name
                credentials[count][0] = scan.next();
                credentials[count][1] = scan.next();

//get original pass from file
                String l[] = scan.nextLine().split("\"[ ]+");
                l[0] = l[0].trim();
                l[0] = l[0].replace("\"", "");

                credentials[count][2] = l[0];
                credentials[count][3] = l[0].trim();
                count++;
            }

//ask for user input
            Scanner scanio = new Scanner(System.in);
            boolean RUN = true;
            int tries = 0;

            while (RUN) {
                System.out.println("**WELCOME**");
                System.out.println("1) Login");
                System.out.println("2) Exit");

                int ch = Integer.parseInt(scanio.nextLine().trim());

                if (ch == 1) {

//increment number of attempts
                    tries++;

//ask for username and password
                    System.out.print("Input username:");
                    String username = scanio.nextLine();
                    System.out.print("Input password:");
                    String password = scanio.nextLine();

//generate hash
                    MessageDigest md;
                    md = MessageDigest.getInstance("MD5");
                    md.update(password.getBytes());
                    byte[] digest = md.digest();
                    StringBuilder sb = new StringBuilder();
                    for (byte b : digest) {
                        sb.append(String.format("%02x", b & 0xff));
                    }
                    String hPassword = sb.toString();

                    boolean badUser = true;
                    for (int i = 0; i < count; i++) {
                        if (username.contentEquals(credentials[i][0])) {
                            if (hPassword.contentEquals(credentials[i][1])) {
//if everything looks good. login
                                List<String> data = null;


//check type of user and print
                                switch (credentials[i][3]) {
                                    case "zookeeper":
                                        data = Files.readAllLines(Paths.get("zookeeper.txt"), Charset.defaultCharset());
                                        break;
                                    case "admin":
                                        data = Files.readAllLines(Paths.get("admin.txt"), Charset.defaultCharset());
                                        break;
                                    case "veterinarian":
                                        data = Files.readAllLines(Paths.get("veterinarian.txt"), Charset.defaultCharset());
                                        break;
                                    default:
                                        break;
                                }

                                for (String s : data) {
                                    System.out.println(s);
                                }

//reset tries
                                tries = 0;

//asks user whether ot logout or exit
                                System.out.println("\n1) Logout.");
                                System.out.println("2) Exit.");

                                ch = Integer.parseInt(scanio.nextLine().trim());
                                if (ch == 2) {
                                    RUN = false;
                                }

                                badUser = false;
                                break;
                            }
                        }
                    }

                    if (badUser) {
                        System.out.println("Invalid Username or password.");
                    }

                } else {
                    RUN = false;
                    break;
                }

//if too many invalid attemps, close the program
                if (tries == 3) {
                    RUN = false;
                    System.out.println("Too many invlaid attempts.");
                }

            }

        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }


}